Thymic Carcinoid with Adrenocorticotropic Hormone-Producing Ectopic Cushing Syndrome and Empty Sella

Objective: Ectopic Cushing syndrome secondary to thymic carcinoid is a rare disorder that may be difficult to diagnose and manage. Methods: We describe a case of severe Cushing syndrome secondary to a large, adrenocorticotropic hormone (ACTH)-producing thymic carcinoid in a patient with a history of primary hyperaldosteronism. Results: A 43-year-old female with a 20-year history of an aldosterone-secreting adrenocortical adenoma following a right adrenalectomy presented with acute onset of proximal muscle weakness, swelling, facial hirsutism, and severe hypokalemia. Ectopic Cushing syndrome was suspected based on the sudden symptom onset and markedly elevated 24-hour urine cortisol and ACTH levels. Magnetic resonance imaging revealed an empty pituitary sella and a large (7.3 cm) mediastinal mass visible on chest computed tomography. The mass was resected by video-assisted thoracoscopic surgery, resulting in resolution of symptoms and cortisol levels. Pathology assessment confirmed well-differentiated thymic carcinoid with positive ACTH staining. Conclusion: This case highlights the clinical features, challenges in diagnostic work up, treatment modalities, and associated endocrine findings in a thymic carcinoid abutting the heart in a patient presenting with ectopic ACTH secretion.